The invention relates to a storage unit for storing electrical energy. The storage unit comprises at least one energy store.
The storage unit also comprises in accordance with the invention a contact area for dissipating heat to a heat sink. The storage unit comprises at least one heat pipe that is connected to the contact area and is connected to the energy store in such a manner that heat losses that are generated inside the energy store can be dissipated to the contact area by way of the heat pipe.
More heat can be advantageously dissipated from the energy store to the heat sink by means of the heat pipe than, for example, by means of a metal heat conductor, as the heat pipe comprises considerably greater heat conducting properties in comparison to a metallic heat conductor.
The contact area for dissipating heat can be, for example, a component of a cooling element, in particular a metal block, which comprises the contact area for dissipating heat to the heat sink. The cooling element can be connected, for example, to the heat pipe, in particular in the region of an end of the heat pipe.
In a preferred embodiment, the storage unit comprises at least two energy stores. The energy stores are spaced apart from one another by way of an intermediate space, it is further preferred that they are adjacent to one another. The heat pipe is connected to the energy store by way of at least one heat conductor, wherein the heat conductor is arranged in the intermediate space. The heat conductor is preferably in operative contact with at least one energy store that is bordered by the intermediate space. The heat conductor is embodied, by way of example, as a heat conducting plate or a heat conducting block. The plate is by way of example a metal plate, the block is by way of example a metal block.
With the arrangement embodied in this manner, heat can be advantageously dissipated from a hot spot of the energy store in particular from a hotspot of a combination of the adjacently arranged energy stores.
In a preferred embodiment, the heat conductor in particular the plate that is arranged in the intermediate space is embodied in a resilient manner. As a consequence, in the case of a heat-related linear expansion of the energy store along a longitudinal axis of the energy store, heat can be dissipated by way of the heat pipe and the linear expansion of the energy store during heating is compensated for by means of the resilient characteristic of the heat conductor. The heat conductor can be embodied in this embodiment as a resiliently embodied heat conductor, for example, by way of two plates that are arranged in a parallel manner with respect to each other and are mutually connected by way of a leaf spring along the longitudinal direction, wherein the leaf spring is arranged in the intermediate space between the plates that are arranged in a parallel manner.
In a preferred embodiment, at least one electrical connector of the energy store is connected to an electrical contact rail. The electrical contact rail is connected to at least one external electrical connector of the storage unit.
The storage unit is preferably embodied for the purpose of being connected by way of the external electrical connector to a further electrical device, for example to a traction battery or an inverter. The contact rail is connected in a heat conducting manner to the contact area, preferably to the cooling element. Thus, in addition to the heat dissipation from the hotspot by way of the heat pipe, heat from the interior of the energy store can be advantageously dissipated by way of the electrical connectors of the energy store.
The electrical connectors of the energy store are embodied, for example, in each case by way of an electrically conductive layer, in particular a Schoop layer.
In a preferred embodiment, the storage unit comprises a heat conductive cooling element already mentioned previously. The cooling element comprises an externally directed surface region that embodies the contact area.
In a preferred embodiment, the energy store is a capacitor. The capacitor is, for example, a rolled-type capacitor or a super capacitor. It is preferred that electrical connectors of the energy store are embodied by way of an electrically conductive layer, in particular a Schoop layer.
The energy store in a different embodiment is a battery. The battery is, for example, a nickel metal hydride battery, a lead acid battery, a lithium ion battery, a lithium polymer battery or a lithium iron phosphate battery, which can be advantageously quickly charged with large currents and discharged.
A combination of individually different energy stores that are components of the storage unit is also feasible. By way of example, the storage unit can comprise at least one battery as an energy store and at least one capacitor as an energy store.
In a preferred embodiment, the electrical connector of the energy store, in particular the electrically conductive layer, is connected to the contact rail in an electrical and heat conducting manner. For this purpose, the contact rail can be connected to the electrically conductive layer for example by means of at least one welded connection or a soldered connection.
It is preferred that the heat pipe is embodied to absorb heat in the region of one end and to dissipate heat in the region of an opposite-lying end by means of a physical state change of the fluid that is enclosed in the heat pipe. The heat pipe comprises by way of example a low pressure in the interior in comparison to an atmospheric standard pressure of 1013 hectopascal, so that a boiling point and/or a dew-point of the enclosed fluid and thus a temperature working range of the heat pipe is fixed in dependence upon the low pressure.
In a preferred embodiment, the heat pipe comprises at least one fluid-filled tube. The fluid is by way of example water, ammonium, alcohol, in particular ethanol or isopropanol.
In a preferred embodiment, the heat conductor is connected in a heat conducting manner to the heat pipe on a longitudinal section of the heat pipe by means of a guide bushing, wherein the guide bushing is embodied to hold the heat pipe in place in a resilient and heat conducting manner in such a manner that the guide bushing can be moved back and forth along a longitudinal extension of the heat pipe. As a consequence, the heat conductor cannot rip or break in the region of a connection site to the heat pipe in the case of a heat expansion of the energy store.
In a different advantageous embodiment, the heat pipe is embodied in a planar manner. It is further preferred that the heat pipe comprises a cross-section, wherein a cross-section width is greater than a cross-section height. The heat pipe can therefore be arranged in a cuboid-shaped storage unit in an advantageously space-saving manner. It is preferred that a ratio of cross-sectional width to cross-sectional height of the cross-section of the heat pipe that is embodied in a planar manner amounts to 30 to 1. A cross-section height of the heat pipe that is embodied in a planar manner amounts by way of example to between 1 millimeter and 3 millimeters.
The storage unit is by way of example an intermediate circuit capacitor of an electrical drive of an electric vehicle. In a different embodiment, the storage unit is an intermediate circuit capacitor of a solar inverter.